This invention relates to image displays and more particularly to enhancing the realism of images by creating an illusion of environmental lighting effects from and on the images.
The present invention relates to the field of optics, and this application makes use of several terms of art used throughout the field. The inventors have adopted and use the following definitions, and they are therefore included in this patent. A xe2x80x98real imagexe2x80x99 is an optical image formed of real foci (Merriam-Webster""s Online Collegiate Dictionary). In other words, real images are made by light rays that are brought to a focus at the image position, and therefore can be made visible on a surface, such as a screen or smoke. See Warren J. Smith, Modem Optical Engineering, 8 (McGraw-Hill 1966). A xe2x80x98virtual image,xe2x80x99 on the other hand, is an image formed of points from which divergent light rays seem to emanate without actually doing so (Merriam-Webster""s Online Collegiate Dictionary) . For example, the virtual image in a plane mirror is at some distance behind the mirror. Virtual images cannot be made visible on a screen because they are made by light rays that do not actually come from the location at which the image appears. See Warren J. Smith, Modem Optical Engineering, 9 (McGraw-Hill 1966). As used throughout the specification, a xe2x80x98negative imagexe2x80x99 is a negative of an image, or an image having the light and dark parts in approximately inverse order to those of the original subject (Merriam-Webster""s Online Collegiate Dictionary). A negative image may be created by reversing the polarity of an image, digital signal processing, or forming a two-dimensional xe2x80x98gobo,xe2x80x99 which is an opaque cut-out resembling the original subject to be placed near a light source. A xe2x80x98focal planexe2x80x99 is a plane that is perpendicular to the axis of a lens or mirror and passes through the focus of the lens or mirror (Merriam-Webster""s Online Collegiate Dictionary).
Movies, slides, video, and other displayed images have long been a major source of audience entertainment. Much effort has been expended to make images appear more like objects in three-dimensional space in order to make them more compelling to the viewer, and thereby increase the entertainment value of such images. A variety of techniques have been employed to cause displayed images to appear more like objects in three-dimensional space. One technique is to create xe2x80x9caerialxe2x80x9d images, which are virtual images that are projected into free space, producing the illusion of a three-dimensional hologram. Such virtual images are typically created using concave mirrors and positive lenses that form images of, for example, physical objects, film projections or video screens. Examples of such a technique can be found in Krause et al., U.S. Pat. No. 5,944,403 and Orlandi, European Patent No. EP-B1-0 410 968.
Another technique to enhance the illusion of realism of displayed images is to clearly establish the distance between the viewer and the image to create an illusion of image depth. One method for creating such an illusion is to place physical objects near the plane of focus of the image in order to establish the relative depth from the image and the object to the viewer. Another method is to place a semi-transparent scrim between the optical objective and the image, and to project an image on the scrim that emphasizes the position of the image relative to the scrim.
Although these techniques succeed to one degree or another in making images more compelling, the images still appear unrealistic because the lighting in and around the images does not match the surrounding environment. In particular, images do not cast a shadow on their surroundings, nor do they contain shadows or reflect lighting effects from light sources in their environments.
To overcome the limitations in the prior art described above, the present invention discloses a system and method for enhancing the realism of displayed images by reflecting lighting effects from the displayed image""s environment in and around the image.
Specifically, in one embodiment of the invention, the system comprises an image display subsystem and a shadow projector. The image display subsystem may be, for example, a virtual or real image projector or video display, and it may display an aerial image or a real image. The shadow projector may be, for example, a slide, film, or video projector or a theatrical lighting fixture with gobo. The shadow projector projects a second image, which may be from a photographic negative or an inversion of the signal of the displayed image, near the displayed image such that the second image appears to be a shadow of the displayed image. Since real shadows are created only by physical objects, the displayed image appears more like an object in three-dimensional space.
The xe2x80x9cshadowxe2x80x9d projected by the shadow projector can be made to correspond with the shape, alignment, movement, and perspective of an object or image relative to a real or virtual light source. By a xe2x80x9cvirtual light source,xe2x80x9d the inventors mean a light source within an image. For example, a virtual light source may be a sun projected on a movie screen. With a second image source comprising fixed media, for example, a gobo or slide, the source can be changed in discrete steps with the movement of a light source or the image. When the second image source comprises continuous media, for example, video or film, the image correspondence may take place continuously. By corresponding the shadow image to the displayed image, the image appears to cast a realistic shadow, further enhancing the illusion of realism.
In another embodiment of the invention, the displayed image contains a virtual light source. The shadow projector projects a shadow near either an object image within the displayed image or a real object near the displayed image, such that the xe2x80x9cshadowxe2x80x9d appears to be cast from the virtual light source. This creates an illusion that the virtual light source is a real light source, and further enhances the realism of the image.
An alternative embodiment comprises an image display subsystem and a first image source. The lighting and shadows from light sources and physical objects in the viewer""s environment are integrated into the image. When displayed, the image contains realistic lighting and shadows from the viewer""s environment. This enhances the realism of the display by creating an illusion that the image is lighted by the environmental light sources or shadowed by real objects in its environment.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.